1. G.C. Lancini and E. Lazzari: Experientia 21, 83 (1965).
2. B. Cavalleri, R. Ballotta and G.C. Lancini: J. Het. Chem. 9, 979 (1972).
3. A.G. Beaman, W. Tautz, T. Gabriel and R. Duschinsky: J. Am. Chem. Soc. 87, 389 (1965).
4. A. G. Beaman, R. Duschinsky and W. P. Tautz (Hoffmann-La Roche Inc.): US Pat. 3,255,201 (7.6.1966) [C.A. 65, 13724 (1966)].
5. D. Lancini, Pavia and E. Lazzari (gruppo Lepetit S. p. A.): US Pat. 3,420,842 (7.1.1969) [C.A. 65, 724 (1966)].